SDP December 2011: What’s New in .NET 4.5 Keynote

Noam and I delivered a joint keynote at the first day of the SDP, covering the new APIs and internal features of .NET 4.5. With my love for internals, I took the easy route of talking about CLR internals and C# 5 async methods, and Noam talked about WCF, Entity Framework, WPF, ASP.NET MVC, and plenty of other frameworks which have been updated in .NET 4.5.

As you probably know, .NET 4.5 is an in-place update for .NET 4.0, which means—as far as Microsoft is concerned—that it should work seamlessly where .NET 4.0 does, with full backwards compatibility. Indeed, I’ve taken the plunge and installed Visual Studio 11 Developer Preview (which ships with .NET 4.5) on my primary laptop and desktop, and haven’t run into any trouble during the last >2 months.

I spent a large part of my 20 minutes talking about C# 5 async methods, which are definitely on their way to becoming my favorite C# feature. It’s going to be very hard to imagine how we used to work directly with continuations and marshaling work back to the UI thread after the dust settles and Visual Studio 11 is released. I haven’t had time to show much more than the simple examples, but I’m pretty sure the potential was clear:

async void DownloadLargeFile(string url) {
  _cts = new CancellationTokenSource();
  try {
    byte[] result = await DownloadAsync(url, cts.Token);
    PlayMovie(result);
  } catch (OperationCanceledException) {
    UpdateStatus("Download canceled.");
  }
}
void CancelDownload() { _cts.Cancel(); }

(Async method with cancellation support and exception handling, all covered by the C# 5 compiler. To run this sample, you will need the Visual Studio 11 Developer Preview.)

During the last few minutes of the talk I focused on the latest CLR performance improvements: concurrent background server GC, multi-core background JIT, automatic NGEN, and managed profile-guided optimization. Currently there aren’t many resources on this topics lying around, but the //build session is pretty good and detailed.

It’s the first CLR release in >5 years that brings serious news from the performance front, especially w.r.t. compilation time penalty. I am looking forward to testing the final bits on production systems to see how startup time and CPU utilization are affected by these impressive features.

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